Abstract: Diffraction gratings based on molecularly imprinted polymer (MIP) were developed as a new sensing strategy for 2,4-dichlorophenoxyacetic acid (2,4-D) detection. Photoinduced surface-relief-gratings (SRGs) on azo polymer films were used as a master to fabricate the MIP gratings. For the fabrication, SRGs were inscribed by irradiation with interfering Ar+ laser beams and the elastomeric stamps were obtained by replica-molding against the SRG-bearing masters. The MIP gratings were produced by microcontact printing with the stamps and in situ photo-polymerization/crosslinking of a functional monomer (4-vinyl pyridine, 4-VP), template (2,4-D), crosslinker (ethyleneglycol dimethacrylate), and photo-initiator in a mixed methanol/H2O solution. The quantitative detections of 2,4-D were achieved by monitoring the variations of diffraction efficiencies of the gratings, which varied with the 2,4-D concentrations in solutions. The diffraction efficiency (DE) variation was triggered by the binding between 2,4-D molecules and caves formed by 4-VP structural units in the MIP. The saturated diffraction efficiency (DE/DE0) was observed to be linearly correlated with the 2,4-D concentration in the testing range. The methodology developed in this study for 2,4-D detection shows excellent sensitivity with the fast response, high selectivity from the analogous compounds, continuous sensing ability and reusabilityTemplate and target information:2,4-dichlorophenoxyacetic acid, 2,4-DAuthor keywords:Surface-relief-grating, molecularly imprinted polymer, 2,4-Dichloropheoxyacetic acid, detection